“Vaccines are very effective, but there is a small failure rate,” said Dr. Rob Schechter, chief of immunization at the state Department of Public Health. “When the whole population is highly immunized, the few vulnerable children are protected by the immunity of the community. But when there is a high rate of exemptions, diseases can spread even to people who are immunized.”

The effects of this high rate of exemptions, many of which are requested by younger parents who may not be familiar with the consequences of vaccine prevented diseases, are starting to show.

An outbreak of chicken pox affected more than 40 students at the Lagunitas and San Geronimo Valley elementary schools in 2007, where 17 and 57 percent of students had received personal belief exemptions from vaccination. In addition, the Lagunitas School District excluded about 70 students from the two schools for three weeks out of concern that they were at high risk of contagion. Many of them had never been vaccinated.

Rogers quotes sources on both sides of the vaccine debate, including public health professionals, parents and a chiropractor who said “Vaccination is based on the medical fallacy that our bodies are stupid … The truth is that the body has a nearly infinite capacity to protect itself against infection as well as other diseases. When I was a kid, everybody got measles, mumps or chicken pox, and nobody died.”